The invention relates to a control assembly consisting of an operating cable and a drive member, and to a process for the manufacture of a connection which resists the tensile and/or torsional forces applied between the drive member and the operating cable.
In control assemblies of this type the operating cable must be connected without play to the drive member. These assemblies are used especially in motor vehicle window raising means and sliding tops, as known for example from U.S. Pat. Nos. 4,056,274 and 4,081,926, and British Pat. No. 1,184,268. The drive member is usually made of plastic, and the operating cable comprises a core made of a plurality of wires twisted together and preferably covered with polyamide. The so-covered core is provided with a spiral winding of relatively thick and rigid wire, and a uniform spacing is maintained between adjacent wire turns. At the end of the operating cable a length of the core is free of wire winding, and this length is rigidly connected to the drive member. A drive pinion meshes between the wire turns and is rotated by a crank or a motor, especially an electric motor. The pinion is guided in the intervals between the wire turns as in a screw or worm. The operating cable of the control assembly is moved in the axial direction by the rotation of the pinion, and the drive member, mounted for example on a sliding top or on the frame of a window pane, is pulled or pushed. Therefore, the connection between the core of the operating cable and the drive member must absorb the tensile forces necessary to move the sliding top or window pane.
Together with the axial forces, the rotating pinion transmits tangential forces to the operating cable, and these forces are re-transmitted to the connection between the operating cable core and the drive member. Therefore the connection must resist this axial and radial double load for a long time.
The motion of a sliding top generally requires two parallel control assemblies to pull or push the sliding top simultaneously. To avoid sliding top deviations, the control assembly must be provided with high longitudinal precision and narrow tolerances in the connection between the operating cable core and the drive member. To date, this has entailed great difficulties, and known connections are unsatisfactory especially in respect to radial moment absorption.
According to the prior art, the connection between the operating cable core and drive member is produced so that the operating cable core is passed through a cylindrical sleeve of the drive member and provided with a stop block at the end which has been passed through. The block, mechanically crimped on the operating cable, is about 8 mm long and acts as a limit point for the tensile forces applied to the operating cable. Although the stop block application process frequently produces a degree of axial play between the operating cable and the sleeve, the necessary precision in the length of the connection is substantially obtained, and the tensile forces are absorbed. However, such stop blocks are not sufficient to prevent operating cable rotation in the sleeve of the drive member. To date, to oppose the radial moment, in addition to the use of a stop block, the end of the operating cable is adhesively bonded to the sleeve to provide a connection whose rigidity is sufficient so that the tangential forces are absorbed. But since the adhesive surface is exposed to continuous alternating stress, high grade, expensive adhesives must be used, for example cyanate-base adhesives. Preparation of the surface and careful processing are necessary to obtain a good connection. But even the best adhesive bond can separate. Finally, the double safeguard provided by the different connection means (adhesive and stop block) can be obtained only with an exactly adapted, multi-step process.
The object of the present invention is to provide a minimum-length tolerance control assembly with a play free, high load strength connection resistant to tension and/or torsion between the operating cable core, which is exposed to tensile, shearing, and torsional forces, and a drive member made of plastic. Another object is to achieve a process for the manufacture of such a connection with economy of material and, if need be, in a single operation.
The first part of this object is achieved in accordance with a preferred embodiment by a control assembly in which the core of the operating cable is welded to the drive member sleeve in tension and/or torsion resistant conditions.
The characteristic feature of the process for the production of the connection between the plastic drive member and the core wire of the operating cable consists in the ultrasonic welding of the two parts. In an especially advantageous embodiment of the process the drive member is mechanically compressed with the operating cable core during the ultrasonic welding operation.
The process of the invention results in a reliable connection which is eminently superior to conventional control assemblies in respect to axial and transverse stress resistance. The process eliminates the use of high cost adhesives and in some cases also of the heretofore necessary end block. An extremely strong connection resisting all shearing, tensile, and radial forces is provided between the operating cable and the drive member.
These and further objects, features and advantages of the present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, several embodiments in accordance with the present invention.